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ARTICLE ON EFFICIENT USE OF LIDAR DATA FOR INFRASTRUCTURE AND UTILITIES

In recent years the demand for high accuracy laser data within the infrastructure sector has increased. The market has discovered the benefits of using both existing off-the-shelf laser data, and to ordering new laser data capture suited for high accuracy planning, building and maintenance. “We are not only talking about reduced costs but also about the opportunity to construct secure and more lasting solutions from an accurate geographic source”, says Henrik Åquist, new CEO of Blom Sweden AB.

The challenge of laser data is using the right laser data for the right purpose. For example, laser data that Blom collects on behalf of Lantmäteriet in the project New National High model (NNH) can be used for a general study in infrastructure projects. However, for projects demanding a high accuracy, where accuracy on centimeter level is required, helicopter scanned data is better suited.

The biggest demand for laser data in infrastructure projects today are in projects related to roads, railroads, harbors and power lines. For road projects Blom has, with its TopEye technology, been one of the pioneers and major data collectors since the middle of the 1990s.

In those days the laser scanning was on a research and testing level. Since then laser scanning has become standard and is now used in various forms, for example in road administration projects in conjunction with aerial photos. In rail road projects it is of great importance that the collection of data can take place without intruding traffic on the already today busy railroad network.

Power lines are maybe one of the areas where you can utilize laser scanning the most. Everything from basic planning, surface models, ground models, maps, orthophotos and visualizing to completing plans for forest maintenance are useful data. Trees near to the power lines that are at risk may be detected and valuated, consultants may be engaged for cutting dangerous trees down and compensation to the land owner can be paid. New general directives demands that all power line owners shall have their lines documented regarding position of poles and wires. “These demands have put pressure on some of the power line owners. However, the demands can rapidly be arranged as a rotor wing system is able to scan up to 200 km of power line each day”, says Henrik Åquist.

Low point density laser data

Airborne laser scanning has revolutionized the ability to capture highly accurate and expansive ground and surface models due to its ability to force through vegetation and rapid data capture.

The accuracy and abundance of details is due to the number of points collected whilst maintaining a high flying height. When you are talking about laser data that has low point density you often mean point density between 0.2-2 points/m2. For example, this resolution of data is suitable for the early stage planning of a road; deciding on the road layout and what consequences it will have on theenvironment regarding noise, water flow etc.

Examples of low point density include comprehensive laser scanning covering whole municipalities from airplanes, or the “New National Height” model (NNH). Considering the requests from customers there is no doubt that there is a need for low point density laser data.

It can be difficult for a client to know where to use the low density laser data if you’re not familiar with the technology. “In this respect our responsibility as a supplier is crucial”, says Henrik Åquist. “A client only needs to know what usage they want from the product, and it is Blom´s responsibility, with our experience from many projects, to decide on which collection method, point density, flying height etc. is most suitable for the specific project”, continues Henrik Åquist.

High density laser data

With high density laser data you are generally referring to a point density between 5-50 points/m2. The data is usually captured with a helicopter mounted system and, in most cases, includes simultaneous capture of aerial photos.

Although low resolution laser data can have a high accuracy the model has deficiencies as real world objects between the laser points are not shown. On the other hand, a high density scan has so little space between the points that all important infrastructure and details can be modeled. For road and railroad projects, height models with accuracy down to 2 cm can be reached.

There are also other areas that require high point density data, with power lines being a good example. Mapping towers and cables demand high requirements. At the same time, detecting potential trees that threaten to grow or fall into line is vital information. In these cases the use of laser scanning with low point density and accuracy can have devastating consequences.

As shown above high density laser data can be used to create detailed models of power lines, suitable for 3D visualizations. The aerial photography, often captured at the same time, is used for detailed inspection of all the parts of the power line, such as isolators and mounting points.

For more information on laser scanning and Blom's services, please contact Dag Solberg